fsolve stopped because it exceeded the function evaluation limit, options.Ma​xFunctionE​valuations = 400 (the default value).

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Bassem Essam
Bassem Essam 2020-12-31
评论： Walter Roberson 2020-12-31
So I am trying to solve system of equations using fsolve but the message above keeps showing, here is my code
clc; clear; close all;
global X L2 t2 t1 h
L2= 4.42;
X= 4; t2= 100*pi/180; t1=50*pi/180; h=0.5; %initial values%
x= fsolve(@SiccorLift,[X;t2;t1;h]);
X= x(1); t2= x(2)*180/pi; t1= x(3)*180/pi; h= x(4);
function F= SiccorLift(x)
global L2
F(1) = x(1) + L2*cos(x(2)) - 5*cos(x(3));
F(2) = L2*sin(x(2))- 5*sin(x(3));
F(3)= x(1)+ 8*cos(x(3));
F(4)= 8*sin(x(3)) - x(4);
end

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Walter Roberson
Walter Roberson 2020-12-31
  2 个评论
Walter Roberson
Walter Roberson 2020-12-31
Ran in:
format long g
L2= 4.42;
X = 4+1i; t2 = 100*pi/180 + 1i; t1 = 50*pi/180 + 1i; h=0.5; %initial values%
options = optimoptions(@fsolve, 'MaxFunctionEvaluations', 10000, 'MaxIterations', 10000);
x= fsolve(@(x)SiccorLift(x,L2), [X;t2;t1;h], options);
Equation solved. fsolve completed because the vector of function values is near zero as measured by the value of the function tolerance, and the problem appears regular as measured by the gradient.
X= x(1); t2= x(2)*180/pi; t1= x(3)*180/pi; h= x(4);
disp(X)
2.96133921023046e-11 + 1.55828966080547i
disp(t2)
90.0000000007112 + 31.2519208822566i
disp(t1)
90.0000000002143 + 11.0910318354747i
disp(h)
8.15035377555743 - 1.20326062635646e-12i
function F= SiccorLift(x, L2)
F(1) = x(1) + L2*cos(x(2)) - 5*cos(x(3));
F(2) = L2*sin(x(2))- 5*sin(x(3));
F(3)= x(1)+ 8*cos(x(3));
F(4)= 8*sin(x(3)) - x(4);
end
You can get exact solutions; MATLAB thinks there are four of them, whereas Maple says there are two solutions.
... Yes, this does mean that the complex results are not accidents: the exact solutions are complex-valued.

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